Mandrels and other work holding media



Feb. 27, 1968 A. E. SYKES 3,370,842

MANDRELS AND OTHER WORK HOLDING MEDIA Filed Nov. 30, 1965 5 Sheets-Sheet1 FIGJ A. E. SYKES MANDRELS AND OTHER WORK HOLDING MEDIA Feb. 27, 1968 3Sheets-Sheet 2 Filed Nov. 50, 1965 1 i L Isl KPQ Feb. 27, 1968 A. E.SYKES MANDRELS AND OTHER WORK HOLDING MED' IA 5 Sheets-Sheet 3 FiledNov. 30, 1965 United States Patent 3,370,842 MAYDRELS AND (JTHER WORKHOLDING MEDIA Alfred E. Sykes, 329 Leicester Road, Markfield, Leicester,England Filed Nov. 30, 1965, Ser. No. 510,515 Claims. (Cl. 269-20) Thisinvention relates to mandrels and other work holding media.

According to the present invention there is provided an expandingmandrel, including a relatively non-distortable substantiallycylindrical reactor block having a central bore therein and a relativelydistortable sleeve surrounding the reactor block, there being locatedwithin cylindrical bores disposed radially in the reactor block andcommunicating with the central bore at least three axial rows of thrustunits, each thrust unit being capable of being urged by fluid pressureinto contact with the inner Wall of the sleeve, whereby on fluidpressure being applied to the thrust units the sleeve becomes distortedto increase its effective outside diameter.

In order that the invention may readily be carried into effect, twoembodiments thereof will now be described, by way of example only, andwith reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a work holding device whichincorporates an expanding mandrel in accordance with the presentinvention;

FIG. 2 is a cross-sectional view on the line IIH of FIG. 1;

FIG. 3 is a plan view of a further embodiment of Work holding devicewhich incorporates a plurality of expanding mandrels in accordance withthe invention;

FIG. 4 is an end view of the device illustrated in FIG. 3; and

FIG. 5 is a section on the line V-V of FIG. 3.

Referring first of all to FIGS. 1 and 2 which show a work holding deviceparticularly suitable for face grinding gears, an expanding mandrel inaccordance with the present invention, generally indicated at 1, ismounted on an existing machine table 1a. The expanding mandrel 1includes a relatively non-distortable reactor block 2 which, as will beseen more particularly from FIG. 2, is substantially cylindrical apartfrom flats 3 the purpose of which will be explained later. This reactorblock 2 is made of steel or some other appropriate metal and isrelatively non-distortable in relation to a relatively distortablesleeve 4 which surrounds the reactor block 2. The distortable sleeve 4has an integral base 5 and may be of steel or other suitable metal andhave a wall thickness which is capable of being distorted slightly underinternal pressure from pressure areas. The base 5 is fixed by bolts 6 toa mandrel holder 7 fixed by bolts 8 to the machine table In and passingthrough an aperture 9 therein. Within the reactor block 2 is a centralbore 10 which communicates via ducts 11 with a plurality of cylindricalbores 12 disposed radially in the reactor block 2, each of thesecylindrical bores 12 housing a thrust unit 13 which may consist of ametal disc faced with a disc of a more resilient material, for example,neoprene. Each of the thrust units 13 is adapted to be urged radiallyoutwardly of the reactor block 2 so as to contact the inner surface ofthe sleeve 4. The thrust units 13 are arranged in axial rows and thereare at least three of said rows arranged symmetrically about the reactorblock. In the particular embodiment shown in FIG. 1 there are four suchrows, each arranged at a right angle to the adjacent rows as will beseen in FIG. 2. There should be at least two thrust units in each suchrow and, as will be seen from FIG. 2, in this particular embodimentthere are four such thrust units in each such row.

Located within the central bore 10 is a primary piston 14 for increasingthe fluid pressure within the system. This primary piston 14 is urgedinto its pressure applying position by a spring force and in thisparticular embodiment the spring force is given by a bank of Bellevillewashers 15 hearing at one end against a plug 16 which closes the lowerend of the mandrel holder 7 and at the other end against a head 17 of anoperating rod 18. The lower end of operating rod 18 is provided with asteel pin 19 which engages within recess 20 of a lever 21 pivoted at oneend 22 to a bracket 23 fixed by bolt 24 to machine table In and having aroller 25 at its otherend which co-operates with a cam track 26.

Communicating with central bore 10 is a further bore 27 within which isa secondary piston 28 which is manually operable.

The work holding device illustrated in FIGS. 1 and 2 is oil operated,and, as previously mentioned, is particularly suitable for face grindinggears and one such gear is indicated, by chain-dotted line 29, inposition on the mandrel 1. With oil pressure within the system at aminimum, no distortion will occur to the sleeve 4 and therefore the gear29 may be slipped easily over the mandrel 1, the depth of entry of themandrel 1 into the bore of gear 29 being governed by the position of aregister bush 30. The oil pressure within the system is adjusted bymeans of the secondary piston 28 whereby thrust units 13 are forcedradially outwardly against the inner surface of the deformable sleeve 4but this pressure is not sufficient to distort the sleeve 4 but ismerely a setting-up pressure. The actual gripping force will be suppliedwhen roller 25 (which, in the setting up procedure and in positioningthe work on the mandrel, has been in position 25a indicated by dottedlines) moves over the cam track 26 so that the roller assumes position25. This releases the downward holding force on the operating rod 18and, by virtue of the reaction in Belleville washers 15, the primarypiston 14 is forced upwardly so as to increase the oil pressure withinthe system. This increase in pressure forces the thrust units 13radially outwardly and it will be seen from FIG. 2 the sleeve 4 isdistorted so that the effective outside diameter of the sleeve 4 isincreased. It will be appreciated that in the axial areas where the rowsof thrust units 13 are operating, lobes 31 will be formed and the partsof the sleeve 4 which are intermediate these lobes will move radiallyinwardly. This latter movement is allowed for by the flats 3 previouslyreferred to on the outer surface of the reactor block 2. On roller 25moving into position 25a once again, the operating rod 18 can movevertically downwards and the pressure exerted by primary piston 14 isrelieved, thereby the sleeve 4 reverts to its original ring shape andthe grip on the work is removed.

In the embodiment illustrated in FIGS. 3 to 5, a plurality of expandingmandrels are employed of the same general construction as described inrelation to FIG. 1. These mandrels 1 are all mounted on a casing 32 andare supplied with oil pressure from a common pressure source 33 whichmay be a hand operated pump. Within the casing 32 are common pressuretransmitting ducts 34 and also a pressure indicator 35 may be provided.The pressure indicator 35 may include a pin 36 which is moved for agiven distance to assume the position shown in dotted line 36a when thelocking pressure has been reached in the system. Two secondary pistons37 and 38 may be provided for adjustment purposes only in the same waythat secondary piston 28 was provided in the FIG. 1 embodiment. Also, ahigh pressure hydraulic plug 39 may be included in the system.

A detail of FIG. 3 is shown in FIG. 5 illustrating a gear 40 positionedon the mandrel 1 for face grinding.

constructed in accordance with the present invention, be-" cause each ofthe thrust units is forced outwardly from a common pressure source, thedistortion of the sleeve 4 will be equal at all points where pressure isexerted. Also, there are no places in the mandrel through which swarf ordirt may enter.

The construction of work holding device may be modified within the scopeof the invention as defined in the appended claims, for example, insteadof being oil operated, air or a liquid other than oil may be used as thepressure transmitting medium.

I claim:

1. An expanding mandrel, including a relatively nondistortablesubstantially cylindrical reactor block having a central bore thereinand cylindrical bores disposed radially in the reactor block andcommunicating with the central bore, and a relatively distortable sleevesurrounding the reactor block, there being located within said radiallydisposed bores four axial rows of thrust units symmetrically disposed inthe reactor block, each row consisting of four equally spaced thrustunits; each thrust unit being capable of being urged by fluid pressureinto contact with the inner wall of the sleeve, whereby on fluidpressure being applied to the thrust units, the sleeve becomes distortedto increase its effective outside diameter, the mandrel being furthercharacterized in that the outer surface of the reactor block between therows of thrust units is provided with flats to allow those parts of thedistortable sleeve between the rows of thrust units to distort radiallyinwardly on the effective outside diameter of the sleeve beingincreased.

2. An expanding mandrel which a primary piston for supplying workingfluid pressure to the thrust units is located within the central bore ofthe reactor block, said primary piston being spring urged to apressure-applying position.

3. An expanding mandrel as claimed in claim 2, in which Bellevillewashers are employed to urge the primary piston to the pressure applyingposition, the Belleville washers being held compressed-so that theprimary piston is in the pressure relieved position by an operating rod.

4. An expanding mandrel as claimed in claim 2, in which located within afurther bore which communicates with the central bore of the reactorblock is a secondary piston manually operable for setting the fluidpressure Within the central bore preparatory to the primary piston beingoperated.

5. In a work holding device, an expanding mandrel. as claimed in claim3, in which the operating rod is given as claimed in claim 1, in

6/1943 Jones 8244 x

1. AN EXPANDING MANDREL, INCLUDING A RELATIVELY NONDISTORTABLESUBSTANTIALLY CYLINDRICAL REACTOR BLOCK HAVING A CENTRAL BORE THEREINAND CYLINDRICAL BORES DISPOSED RADIALLY IN THE REACTOR BLOCK ANDCOMMUNICATING WITH THE CENTRAL BORE, AND A RELATIVELY DISTORTABLE SLEEVESURROUNDING THE REACTOR BLOCK, THERE BEING LOCATED WITHIN SAID RADIALLYDISPOSED BORES FOUR AXIAL ROWS OF THRUST UNITS SYMMETRICALLY DISPOSED INTHE REACTOR BLOCKS; EACH ROW CONSISTING OF FOUR EQUALLY SPACED THRUSTUNITS; EACH THRUST UNIT BEING CAPABLE OF BEING URGED BY FLUID PRESSUREINTO CONTACT WITH THE INNER WALL OF THE SLEEVE, WHEREBY ON FLUIDPRESSURE BEING APPLIED TO THE THRUST UNITS, THE SLEEVE BECOMES DISTORTEDTO INCREASE ITS EFFECTIVE OUTSIDE DIAMETER, THE MANDREL EING FURTHERCHARACTERIZED IN THAT THE OUTER SURFACE OF THE REACTOR BLOCK BETWEEN THEROWS OF THRUST UNITS IS